31 

 application of 2,4-D to waterhyaci nths noted "no adverse effects to 

 water fauna" during and after the application of 2,4-D. After over 

 30 years of continuous use in aquatic environments, monitoring continues 

 to indicate no adverse effects to water fauna due directly to 2,4-D 

 (Smith and Isom, 1967; Whitney et al . , 1973; Moore, 1974). 



Mode of Action 



The mode of action of 2,4-D has been studied more than any other 

 herbicide (Ashton and Crafts, 1973; Mullison, 1982). Most reviews of the 

 mode of action of 2,4-D indicate that it affects almost every biological 

 activity of a plant (Brian, 1964; Cams and Addicott, 1964; Kiermayer, 

 1964; Wort, 1964a; Ashton and Crafts, 1973; and Mullison, 1982). 

 However, the primary mechanism and site of action has not been clearly 

 established (Ashton and Crafts, 1973, Weed Science Society of America, 

 1979; Black and Buchanan, 1980; Mullison, 1982). Van Overbeek (1964) 

 and Black and Buchanan (1980) suggested that the growth of a plant is 

 regulated by rhythmic fluctuations in levels and locations of 

 plant growth substances. This fluctuation is interrupted by 2,4-D and 

 orderly plant development is altered. Immature cytoplasm is pre- 

 vented from maturing and mature cytoplasm reverts back to an immature 

 physiological state (Van Overbeek, 1964). Therefore, 2,4-D can be 

 effective throughout the life of susceptable species, but is especially 

 effective during immature stages when endogenous levels of growth 

 hormones are highest and the plant is actively growing (Black and 



Buchanan, 1980). 



Morphological and physiological responses by plants to 2,4-D depend 

 upon the sensitivity and physiological condition of the treated species 



